1. Field of the Invention
This invention relates to intumescent, halogen-free, silicon-phosphorus-nitrogen (SPN) polymeric flame retardants, a process for their preparation, and compositions and articles into which they are incorporated.
2. Description of the Related Art
Due to the increasing concerns over the environment and fire safety, there has been an effort to develop halogen free flame retardants (HFFR) for use in various polymeric systems. Phosphorus and nitrogen based intumescent flame retardant (IFR) systems are widely used. However, by incorporation of high loadings of flame retardant (FR) into a polymer matrix, the properties of the polymer composition may be sacrificed, for example physical, electrical, or aging properties. Therefore, there is a demand to reduce the loadings of HFFR in the flame-retardant compositions while maintaining the properties of the polymer matrices. Sometimes, phosphorus and nitrogen based IFR at low molecular weights are used, but suffer from migration of the IFR.